how to save vmcore onto the hard disk

The diskdump utility captures the vmcore onto disk.

diskdumputils package

1. select the dump partition in /etc/sysconfig/diskdump
2. format the dump partition
# service diskdump initialformat
3. enable the service
# chkconfig diskdump on
# service diskdump start
4. verify whether diskdump enabled
If /proc/diskdump exists and it shows the registered dump device, the diskdump has been activated.
# cat /proc/diskdump
5. testing diskdump
To test diskdump, use Alt-SysRq-C or "echo c > /proc/sysrq-trigger". After completing the dump, a vmcore file will be created during the next reboot sequence, and saved in a directory of the name format :
/var/crash/127.0.0.1

crash utility can be used to analyse it.